U.S. patent application number 17/626227 was filed with the patent office on 2022-08-18 for n-alkyl-d-glucamine based macroporous polymeric cryogel for sequestering and/or removing toxic contaminants.
This patent application is currently assigned to CONSIGLIO NAZIONALE DELLE RICERCHE. The applicant listed for this patent is ALMA MATER STUDIORUM UNIVERSITA' DI BOLOGNA, CONSIGLIO NAZIONALE DELLE RICERCHE. Invention is credited to Daniele CARETTI, Sabrina Carola CARROCCIO, Francesca CUNSOLO, Tommaso MECCA, Vittorio PRIVITERA, Stefano SCURTI, Martina USSIA.
Application Number | 20220259075 17/626227 |
Document ID | / |
Family ID | |
Filed Date | 2022-08-18 |
United States Patent
Application |
20220259075 |
Kind Code |
A1 |
CARROCCIO; Sabrina Carola ;
et al. |
August 18, 2022 |
N-ALKYL-D-GLUCAMINE BASED MACROPOROUS POLYMERIC CRYOGEL FOR
SEQUESTERING AND/OR REMOVING TOXIC CONTAMINANTS
Abstract
The disclosure relates to N-alkyl-D-glucamine based macroporous
polymeric cryogels with three-dimensional structure and with
interconnected pores, which are used for sequestering and/or
removing toxic contaminants, such as toxic metalloids and/or toxic
heavy metals, for example from water and/or soil and the method for
the preparation of said -alkyl-D-glucamine based macroporous
polymeric cryogels.
Inventors: |
CARROCCIO; Sabrina Carola;
(CATANIA, IT) ; CUNSOLO; Francesca; (CATANIA,
IT) ; MECCA; Tommaso; (CATANIA, IT) ;
PRIVITERA; Vittorio; (CATANIA, IT) ; USSIA;
Martina; (CATANIA, IT) ; CARETTI; Daniele;
(BOLOGNA, IT) ; SCURTI; Stefano; (BOLOGNA,
IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CONSIGLIO NAZIONALE DELLE RICERCHE
ALMA MATER STUDIORUM UNIVERSITA' DI BOLOGNA |
ROMA
BOLOGNA |
|
IT
IT |
|
|
Assignee: |
CONSIGLIO NAZIONALE DELLE
RICERCHE
ROMA
IT
ALMA MATER STUDIORUM UNIVERSITA' DI BOLOGNA
BOLOGNA
IT
|
Appl. No.: |
17/626227 |
Filed: |
July 13, 2020 |
PCT Filed: |
July 13, 2020 |
PCT NO: |
PCT/EP2020/069695 |
371 Date: |
January 11, 2022 |
International
Class: |
C02F 1/28 20060101
C02F001/28; B01J 20/26 20060101 B01J020/26; B01J 20/28 20060101
B01J020/28 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2019 |
IT |
102019000012339 |
Claims
1. A macroporous polymeric adsorbent material having a
three-dimensional structure with interconnected pores of diameter
comprised between 5 and 100 pm, being in the form of a cryogel,
wherein the cryogel is of formula (I): ##STR00014## wherein n is a
percentage comprised between 0 and 99; m is a percentage comprised
between 1 and 100; n+m is 100; p is a value ranging from 0% to 40%
of (n+m); Y is selected from the group consisting of: COOH,
COOCH.sub.2CH.sub.2OH, COOCH.sub.2CH.sub.2NH.sub.2, S0.sub.3H,
PhS0.sub.3H, and PhCOOH; R is selected from the group consisting of
H, CH.sub.3, CH.sub.2CH.sub.3, CH.sub.2CH.sub.2CH.sub.3, and
CH(CH.sub.3).sub.2; R', R'', R'.sup.1' are independently selected
from H or CH.sub.3; spacer is selected from the group consisting of
##STR00015## where q is an integer comprised between 1 and 10; A is
the main polymeric chain which is repeated as indicated in the
general formula (I); and the crosslinker is selected from the group
consisting of: N,N'-Methylenebisacrylamide, N,
N'-Methylenebismetaacrylamide, N,N'-hexamethylenebisacrylamide, N,
N'-diallylbisacrylamide, diallyl fumarate, diallyl phthalate
ethyleneglycoldiacrylate poly (ethyleneglycol) diacrylate
propyleneglycoldiacrylate poly (propyleneglycol) diacrylate.
2. The macroporous polymeric adsorbent material according to claim
1 wherein the interconnected pores have a diameter of 20-30 pm or
5-10 pm, or having a porosity comprised between 50% and 95%; or
porosity is comprised between 80% and 90%; or n is 0%, 25%, 50%, or
75%; or m is 100%, 75%, 50%, or 25%; or p is 10%, 16.7%, or 20%; or
Y is COOCH.sub.2CH.sub.2OH, or COOCH.sub.2CH.sub.2NH.sub.2; or R is
CH.sub.3; or R', R'', and R'.sup.1' independently selected from H
or CH.sub.3; or the spacer is ##STR00016## or q is 1 or 2.
3.-12. (canceled)
13. The macroporous polymeric adsorbent material according to claim
1 having a porosity comprised between 80% and 85% wherein the
interconnected pores have a diameter comprised between 20 and 30
pm, and the cryogel of formula (I) is a crosslinked
polystyrene-N-methyl-D-glucamine.
14. The macroporous polymeric adsorbent material according to claim
1 having a porosity comprised between 82% and 87% wherein the
interconnected pores have a diameter comprised between 10 and 15 pm
and the cryogel of formula (I) is a crosslinked copolymer of
polystyrene-N-methyl-D-glucamine and 2-hydroxyethylmethacrylate
copolymer 1:1.
15. A process for the preparation of macroporous polymeric
adsorbent material having a three-dimensional structure with
interconnected pores of diameter comprised between 5 and 100 pm
being in the form of a cryogel, wherein the cryogel is of formula
(I): ##STR00017## wherein n is a percentage comprised between 0 and
99; m is a percentage comprised between 1 and 100; n+m is 100; p is
a value ranging from 0% to 40% of (n+m); Y is selected from the
group consisting of: COOH, CONH.sub.2, COOCH.sub.2CH.sub.2OH,
COOCH.sub.2CH.sub.2NH.sub.2, COOCH.sub.2CH.sub.2N(CH.sub.3) 2,
S0.sub.3H, PhS0.sub.3H, and PhCOOH; R is selected from the group
consisting of H, CH.sub.3, CH.sub.2CH.sub.3,
CH.sub.2CH.sub.2CH.sub.3, and CH(CH.sub.3).sub.2; R', R'',
R'.sup.1' are independently selected from H or CH.sub.3; spacer is
selected from the group consisting of ##STR00018## where q is an
integer comprised between 1 and 10; A is the main polymeric chain
which is repeated as indicated in the general formula (I); and the
crosslinker is a compound with two polymerizable double bond, the
process comprising the following steps: a) mixing at least one
polymerizable monomer containing N alkyl-D-glucamine selected from
the group consisting of: ##STR00019## wherein R is selected from
the group consisting of H, CH.sub.3, CH.sub.2CH.sub.3,
CH.sub.2CH.sub.2CH.sub.3, and CH(CH.sub.3).sub.2; R' is H or
CH.sub.3 q is an integer comprised between 1 and 10; and optionally
a polymerizable monomer not containing N-alkyl-D-glucamine selected
from the group consisting of: ##STR00020## wherein R is selected
from the group consisting of H, CH.sub.3, CH.sub.2CH.sub.3,
CH.sub.2CH.sub.2CH.sub.3, and CH(CH.sub.3).sub.2; R' is H or
CH.sub.3 q is an integer comprised between 1 and 10; with a
crosslinking agent having two polymerizable double bonds in the
presence of a solvent or mixture of solvents being in the solid
state at the temperatures used in the cryo-polymerization process;
b) adding at a temperature comprised between 0 and 5.degree. C.,
under stirring, to the solution as obtained in step a) an initiator
of radical polymerization and a catalyst for the production of
radicals; c) cooling of the solution as obtained in b) at a
temperature comprised between -10 and -25.degree. C. for a time
comprised between 12 and 48 hours until the cryogel is obtained;
and d) thawing, washing and drying the cryogel as obtained in step
c).
16. The process according to claim 15 wherein in step a) the
concentration of all polymerizable species is comprised between 10%
and 50% in weight in respect to the volume of used solvent,
preferably wherein the concentration of all polymerizable species
is comprised between 10% and 30% in weight in respect to the volume
of used solvent.
17. (canceled)
18. The process according to claim 15 wherein in step a) the
solvent is selected from the group consisting of: water,
dimethylsulphoxide, dioxane, N, N-dimethylacetamide, tert-butanol,
cyclohexane, and mixtures thereof, more preferably is water.
19. The process according to claim 15 wherein in step a) the
crosslinking agent is selected from the group consisting of:
Divinylsulphone, N, N'-Methylenebisacrylamide,
N,N'-Methylenebismetaacrylamide, N, N'-hexamethylenebisacrylamide,
N, N'-diallylbisacrylamide, diallyl fumarate, diallyl phthalate,
ethyleneglycoldiacrylate, poly (ethyleneglycol) diacrylate,
propyleneglycoldiacrylate, poly (propyleneglycol) diacrylate.
20. The process according to claim 15 wherein in step a) the
crosslinking agent is added in a molar ratio comprised 0 and 1/2.5
in respect to the molar amount of starting monomers, or the
crosslinking agent is added in a molar ratio in respect to the
molar amount of starting monomers of 1/6; or in step a) pH is in
the range between 6-8.
21. (canceled)
22. (canceled)
23. The process according to claim 15 wherein in step b) the
initiator of radical polymerization is a compound capable of
forming radicals selected from the group consisting of organic and
inorganic peroxides, peracids, azo-compounds, redox or UV
initiators.
24. The process according to claim 15 wherein in step b) the
initiator of radical polymerization is used with a concentration
between 0.5% and 10% by weight, based on the sum of monomers by
weight.
25. The process according to claim 15 wherein in step b) the
catalyst for the production of radicals is
tetramethylethylenediamine.
26. The process according to claim 15 wherein in step d) the
washing step is carried out by washing sequentially with water,
followed by diluted HCl and finally with mixtures of
H.sub.20/HCl/Et0H wherein the concentration of EtOH progressively
increase up to pure EtOH.
27. The process according to claim 15 wherein in step d) the drying
step is carried out under nitrogen flow and then under vacuum.
28. A method of sequestering and/or removing toxic contaminants
comprising contacting the macroporous polymeric adsorbent material
having a three-dimensional structure with interconnected pores of
diameter comprised between 5 and 100 pm, being in the form of a
cryogel, wherein the cryogel is of formula (I), of claim 1 to the
toxic contaminants.
29. A device for sequestering and/or removing toxic contaminants
comprising the macroporous polymeric adsorbent material having a
three-dimensional structure with interconnected pores of diameter
comprised between 5 and 100 pm, being in the form of a cryogel,
wherein the cryogel is of formula (I), of claim 1.
30. The method according to claim 28 wherein the contacting the
microporous polymeric absorbent material to the toxic contaminates
comprises contacting the microporous polymeric absorbent material
to water and/or soil contaminated with the toxic contaminants.
31. The method according to claim 28, wherein the toxic
contaminants are toxic metalloids and/or toxic heavy metals.
32. The method according to claim 31 wherein the toxic metalloids
are selected from the group consisting of arsenic, boron, and
antimony, and wherein the toxic heavy metals are selected from the
group consisting of cadmium, mercury, lead, manganese, chromium,
cobalt, nickel, copper, zinc, silver, thallium.
33. (canceled)
34. The device of claim 29 comprising one or more of a filter or a
sponge comprising the macroporous polymeric adsorbent material.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention refers to the field of chemistry and
in particular to a N-alkyl-D-glucamine based macroporous polymeric
cryogel, the method for the preparation thereof and its use for
sequestering and/or removing toxic contaminants such as metalloids
and/or toxic heavy metals, for example from water and/or soil.
PRIOR ART
[0002] Arsenic (As) is a highly toxic and fatal element for human
health. Among the 21 countries in different parts of the world
affected by groundwater arsenic contamination, the largest
population at risk is in Bangladesh, followed by West Bengal in
India. Gravity is such that in Bangladesh there is "the greatest
mass poisoning of a population in history" (M. Argos, T. Kalra, P.
J. Rathouz, Y. Chen, B. Pierce, F. Parvez, T. Islam, A. Ahmed, M.
Rakibuz-Zaman, R. Hasan, G. Sarwar, V. Slavkovich, A. van Geen, J.
Graziano, H. Ahsan, Arsenic exposure from drinking water, and
all-cause and chronic-disease mortalities in Bangladesh (HEALS): a
prospective cohort study, Lancet, 2010, 376, 252-258).
[0003] According to the World Health Organization, the maximum
recommended limit in drinking water is 0.01 ppm. This limit, in
developing nations, is largely exceeded, putting at risk the health
of more than 45 million people. In the last decade, for the removal
of As, adsorption method represents one of the most promising tool
(D. Mohana & C. U. Pittman Jr., Arsenic removal from
water/wastewater using adsorbents-A critical review, J. Hazard.
Mater., 2007, 142, 1-2, 1-53).
[0004] The advantages of adsorption, in addition to the absence of
toxic sludge production, lie in its high removal efficiency and low
cost. Adsorption can be carried out by different types of compounds
such as activated carbon, clays, metal oxides, compounds based on
ferrous ions, biomasses and polymer resins (R. Singh, S. Singh, P.
Parihar, V. P. Singh, S. M. Prasad, Arsenic contamination,
consequences and remediation techniques: A review, Ecotoxicology
and Environmental Safety, 2015, 112 247-270).
[0005] The use of absorbent polymers allows to direct their
formulation towards the selective capture of As III and V with all
the benefits deriving from the use of polymeric materials and the
advantage of an easy and economic regeneration.
N-methyl-D-glucamine based resins have aroused great scientific
interest due to their excellent results in terms of capture and
selectivity towards As (V) (L. Dambies, R. Salinaro, & S. D.
Alexandratos, Immobilized N-Methyl-D-glucamine as an
Arsenate-Selective Resin, Environ. Sci. Technol. 2004, 38,
6139-6146).
[0006] The Chinese patent n. CN102266749 discloses a composite
nano-adsorbent for removing arsenic from water and its preparation
by firstly adding a ferrous salt and a manganate to an aqueous
solution of a soluble organic polymer, and performing a redox
reaction to obtain a nano-iron-manganese oxide copolymer precursor.
Then the dispersed composite nano-adsorbent is obtained by adding a
base to the nano-iron-manganese oxide copolymer precursor and aging
it, wherein the organic polymer is wheat starch, corn starch,
starch dextrin, sweet potato powder or polyethylene glycol. The
so-obtained composite nano-adsorbent is dispersed in the water in a
dosage adjusted according to the arsenic concentration of the raw
water as well as the ratio of the trivalent/pentavalent arsenic.
The adsorbent is kept in contact with the water solution for 5-10
min at a stirring speed of 5-50 rpm. Then, 0.5%-2% polyacrylamide
(PAM) or 1%-5% chitosan and EDTA mixture can be added to the water
as organic flocculants.
[0007] US Patent Application, Publication n. US 2013/0186836
discloses a method for the removal of arsenic by the use of a
porous adsorbent which comprises a solid phase with chelating
groups comprising metal ions.
[0008] Chinese patent n. CN105080519 discloses an adsorbent thin
film retaining hexavalent chromium ions containing
N-methyl-D-glucamine and its method of preparation wherein the
N-methyl-D-glucamine functional resin is synthesized.
[0009] Japanese patent n. JPS58146448 discloses a resin adsorbing
boron obtained by reacting phenols, aldehydes, and aminopolyalcohol
with N-methyl-D-glucamine or N-ethyl-D-glucamine. This
polycondensation reaction, in the presence of an alkaline catalyst,
produces a chelating ion exchange resin having a
three-dimensionally cross-linked structure.
[0010] Japanese patent n. JP2006167638 discloses a method for
removing arsenic from hot spring water by a chelate polymer
comprising N-methyl-D-glucamine and aminopolyol.
[0011] International patent application, publication n.
WO2018180430 discloses a filter cartridge made of a plurality of
filtration base fabrics wrapped around a hollow inner cylinder or
laminated. Part of filter cartridge is constituted by a polyolefin
fiber chemically bonded with N-methyl-D-glucamine, or other
functional groups providing an high efficiency metal-adsorbing.
[0012] International patent application, publication n.
WO2006110574 discloses a method for regenerating
N-Methyl-D-glucamine-functional resin that has been used for
removing boron.
[0013] US Patent Application, Publication n. US 2008/0169240
discloses the preparation of crosslinked polymeric beads for
removing arsenate from water, as well as methods for preparing and
using them, wherein the chelate-forming groups comprise protonated
N-methyl-D-glucamine.
[0014] International patent application, publication n. WO
2017/137919 and US Patent Application, Publication n. 2019/0030494
in the name of the same applicant discloses crosslinked polymeric
materials in the form of cryogel capable of sequestering heparin.
The material is obtained by cryopolymerization, a technique
comprising a freezing step of a solution, being aqueous or a
mixture of polar organic solvents which ensure the solubility of
selected monomers allowing the polymerization in the presence of a
initiator and a crosslinking agent forming a 3D polymeric
material.
[0015] It is known a polymer obtained through radical
polymerization using ammonium persulfate as initiator for glycidyl
methacrylate-N-methyl-D-glucamine monomer (GMA-NMG) able to remove
arsenic in combination with ultrafiltration membranes (Leandro
Toledo, Bernabe L. Rivas, Bruno F. Urbano, Julio Sanchez, Novel
N-methyl-D-glucamine-based water-soluble polymer and its potential
application in the removal of arsenic, Separation and Purification
Technology, V., 2013, 1-7).
[0016] It is known a polypropylene based membrane functionalized by
grafting glycidyl methacrylate and subsequently reacting these
precursor membranes with N methyl-D-glucamine for the selective
removal of arsenic (N. R. Shinde, V. Chavan, R. Acharya, N. S.
Rajurkar, A. K. Pandey, Selective removal of arsenic(V) from
natural water using N-methyl-D-glucamine functionalized
poly(propylene) membranes, J. Env. Chem. Eng., 2, 2014,
2221-2228).
[0017] It is known the formulation of nanocomposite ion-exchange
resins based on N-methyl-D-glucamine groups where organic modified
montmorillonite is used as a filler to improve the mechanical
properties of the material tested to remove arsenate ions in water
solution (B F. Urbano, B. L. Rivas, F. Martinez, S. D.
Alexandratos, Water-insoluble polymer-clay nanocomposite ion
exchange resin based on N-methyl-D-glucamine ligand groups for
arsenic removal, React. Functi. Polym. 72, 2012, 642-649); It is
known a commercially available chelating resin namely, Amberlite
IRA 743 (AMB) consisting in a macroporous polystyrene
N-methylglucamine with free base used to remove chromium(VI) ions
from water solution (M. R. Gandhi, N. Viswanathan, S. Meenakshia,
Adsorption mechanism of hexavalent chromium removal using Amberlite
IRA 743 resin, Ion Exch. Lett. 3, 2010, 25-35);
[0018] Is known a macroporous poly(2-hydroxyethyl
methacrylate)-based monolithic cryogel functionalized with 1-lysine
(pHEMA-lys) obtained by polymerizing hydroxyetyhlmethacrylate
(HEMA) with the crosslinker N--N'-methylenebisacrylamide (MBAA) in
water (R. La Spina et al., "Chemically modified poly(2-hydroxyethyl
methacrylate) cryogel for the adsorption of heparin", Journal of
Biomedical Materials Research, Part B: Applied Biomaterials, vol.
102, no. 6, 2014, 1207-1216).
[0019] The same inventors presented at the XXIII National Congress
of the Associazione Italiana di Scienza e Tecnologia delle
Macromolecole--AIM, 9-12 Sep. 2018, Catania, Italy the results of
arsenate ion capture by materials containing N-methyl-D-glucamine
monomers.
[0020] U.S. Pat. No. 3,567,369 discloses resins for recovering
boron wherein the resin is an insoluble chlorurate cross-linked
copolymer of styrene-divinyl benzene and poly-hydroxy alkyl amine
deriving from sorbitol and mannitol.
[0021] US patent application, publication n. US2011/0117596
discloses macroporous gels being polyacrylamide gel, optionally
modified by iminodiacetic acid, used for absorption of Cu(II).
[0022] International patent application, publication n. WO03031014
discloses macroporous agar and agarose copolymer with a chaotropic
agent used for separating cells, protein and viruses.
[0023] International patent application, publication n. WO03041830
discloses macroporous acrylamide containing copolymers used for the
separation of cells and plasmids.
Technical Problem
[0024] In view of what already known in the art, the present
inventors design a method for the preparation of a macroporous
polymeric adsorbent material able to remove toxic contaminants from
water and soil, having a three-dimensional macroporous structure
significantly improving the performance in terms of adsorption
efficiency and rate of complexation in respect to other known
materials having similar composition but different
three-dimensional structure.
[0025] The process of the invention is based on cryo-polymerization
of a polymerizable monomer containing a residue of
N-methyl-D-glucamine. The cryo-polymerization allows to obtain
macroporous chelating polymers effective in removing toxic
contaminants such as toxic metalloids as arsenic and boron and
other poisoning heavy metals.
[0026] The distinguishing features of the process of the present
invention is the use of cryo-polymerization on N-alkyl-D-glucamine
derivative monomers.
[0027] Unexpectedly the same inventors found that the macroporous
polymeric materials obtained by the process of the present
invention show improved performance in sequestering and adsorbing
contaminants in respect to known materials having similar
composition but different three-dimensional structure.
[0028] The distinguishing feature of the macroporous polymeric
material obtained by the process of the present invention is the
presence of interconnected pores with size diameter ranging from 5
to 100 .mu.m.
[0029] The same inventors performed a purposive selection of
monomers, spacers and cross-linking agent and obtained a polymeric
material with very high porosity and therefore with high
performance in terms of adsorption and rate of complexation.
[0030] Compared to polymeric systems with N-methyl-D-glucamine
already known in the art, the object of the invention has an
excellent surface area availability, which results in considerably
higher sequestrating capacity, and higher adsorption rate towards
toxic contaminants.
[0031] It is possible to modulate the efficiency of the material by
mixing the N-alkyl-D-glucamine derivative monomers with a different
monomer not containing N-alkyl-D-glucamine. The physical properties
of the materials in object can be varied by changing the structure
of monomers used, the crosslinker type and its molar ratio in
respect to the sum of the moles of monomers used, the concentration
of polymerizable species present in the solution, the solvent or
solvent mixtures used to solubilize the monomers, the radical
initiators and catalysts type and concentration used to induce the
polymerization reaction, and finally the temperature used during
the cryo-polymerization process.
[0032] The product obtained makes it easier to dispose of the
residual toxic contaminant through the subsequent leaching of the
system.
OBJECT OF THE INVENTION
[0033] The present invention concerns a macroporous polymeric
adsorbent material having a three-dimensional structure with
interconnected pores of diameter comprised between 5 and 100 .mu.m,
being in the form of a cryogel, wherein the cryogel is of formula
(I):
##STR00001##
[0034] Wherein n is a percentage comprised between 0 and 99;
[0035] m is a percentage comprised between 1 and 100;
[0036] n+m is 100;
[0037] p is a value ranging from 0% to 40% of (n+m);
[0038] Y is selected from the group consisting of: COOH,
CONH.sub.2, COOCH.sub.2CH.sub.2OH, COOCH.sub.2CH.sub.2NH.sub.2,
COOCH.sub.2CH.sub.2N(CH.sub.3) 2, SO.sub.3H, PhSO.sub.3H,
PhCOOH;
[0039] R is selected from the group consisting of H, CH.sub.3,
CH.sub.2CH.sub.3, CH.sub.2CH.sub.2CH.sub.3, CH(CH.sub.3).sub.2;
[0040] R', R'', R''', the same or different are H or CH.sub.3;
[0041] spacer is selected from the group consisting of
##STR00002##
[0042] q is an integer comprised between 1 and 10;
[0043] A is the main polymeric chain which is repeated as indicated
in the general formula (I);
[0044] crosslinker is a compound with two polymerizable double
bond.
[0045] A further object of the present invention is the use of the
above polymeric adsorbent material for sequestering toxic
contaminants.
[0046] A further object of the present invention is the use of the
above polymeric adsorbent material for the removal of toxic
metalloids and/or toxic heavy metals from contaminated water and/or
soil.
[0047] A further object of the present invention is the process for
the preparation of the above polymeric adsorbent material.
[0048] Further features of the present invention will be clear from
the following detailed description with reference to the
experimental results provided and the attached figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1 shows Scanning Electron Microscopy (SEM) images of
cryogel with (A) Polystyrene-N-methyl-D-glucamine (0%
2-hydroxyethylmethacrylate, HEMA), copolymers with (B) 25% HEMA,
(C) 50% HEMA e (D) 75% HEMA.
[0050] FIG. 2 shows in graph Thermal Gravimetric Analysis and its
derivative (TGA and DTGA) profiles of
Polystyrene-N-methyl-D-glucamine and copolymer with 50% HEMA
(continuous and dashed line respectively).
[0051] FIG. 3 shows .sup.1H-NMR spectra of
styrene-N-methyl-D-glucamine monomer in DMSO.
[0052] FIG. 4 shows HMBC spectra of the
styrene-N-methyl-D-glucamine monomer in DMSO.
[0053] FIG. 5 shows Fourier Transform Infrared Spectroscopy (FTIR)
spectra measured on Polystyrene-N-methyl-D-glucamine cryogel.
[0054] FIG. 6 shows in graph the efficiency in arsenic
sequestration as a function of immersion time.
DETAILED DESCRIPTION OF THE INVENTION
Definition
[0055] Within the meaning of the present invention, macroporous
means a material containing pores with diameters bigger than 50 nm,
according to IUPAC recommendations.
[0056] Within the meaning of the present invention, adsorbent
material means a material able to remove, by chemical or physical
phenomena occurring at the interface, some chemical species from a
solution, in particular case from a water solution.
[0057] Within the meaning of the present invention,
cryo-polymerization means the process of obtaining macroporous
polymers by performing a polymerization at temperature below the
freezing point of the solvent used to solubilize the monomers.
[0058] Within the meaning of the present invention cryogel means a
polymeric matrix obtained by cryo-polymerization.
[0059] Within the meaning of the present invention HEMA means
monomer of 2-hydroxyethyl methacrylate.
[0060] Within the meaning of the present invention
polystyrene-N-methyl-D-glucamine means a polymer obtained from the
polymerization of 4-vinyl-benzyl-N-methyl-D-glucamine monomer and a
crosslinking agent.
[0061] Within the meaning of the present invention toxic
contaminant means toxic metalloids and/or toxic heavy metals.
[0062] Within the meaning of the present invention a metalloid is a
chemical element having properties in between those of metals and
non-metals.
[0063] Within the meaning of the present invention toxic metalloids
are arsenic, boron, antimony.
[0064] Within the meaning of the present invention heavy metal is a
metal with high density, high atomic weight or high atomic
numbers.
[0065] Within the meaning of the present invention toxic heavy
metals are selected from the group consisting of cadmium, mercury,
lead, manganese, chromium, cobalt, nickel, copper, zinc, silver,
thallium. More preferably, chromium.
[0066] Object of the invention is a macroporous polymeric adsorbent
material having a three-dimensional structure with interconnected
pores of diameter comprised between 5 and 100 .mu.m, being in the
form of a cryogel, wherein the cryogel is of formula (I):
##STR00003##
[0067] Wherein n is a percentage comprised between 0 and 99;
[0068] m is a percentage comprised between 1 and 100;
[0069] n+m is 100;
[0070] p is a value ranging from 0% to 40% of (n+m);
[0071] Y is selected from the group consisting of: COOH,
CONH.sub.2, COOCH.sub.2CH.sub.2OH, COOCH.sub.2CH.sub.2NH.sub.2,
COOCH.sub.2CH.sub.2N(CH.sub.3).sub.2, SO.sub.3H, PhSO.sub.3H,
PhCOOH;
[0072] R is selected from the group consisting of H, CH.sub.3,
CH.sub.2CH.sub.3, CH.sub.2CH.sub.2CH.sub.3, CH(CH.sub.3).sub.2;
[0073] R', R'', R''', the same or different are H or CH.sub.3;
[0074] spacer is selected from the group consisting of
##STR00004##
[0075] q is an integer comprised between 1 and 10;
[0076] A is the main polymeric chain which is repeated as indicated
in the general formula (I);
[0077] crosslinker is a compound with two polymerizable double
bond.
[0078] Preferably the macroporous polymeric adsorbent material has
a porosity comprised between 50% and 95%, more preferably the
porosity is comprised between 80% and 90%.
[0079] Preferably in the macroporous polymeric adsorbent material
having a three-dimensional structure the interconnected pores have
a diameter of 20-30 .mu.m or 5-10 .mu.m.
[0080] In a preferred embodiment in the macroporous polymeric
adsorbent material having a three-dimensional structure when the
interconnected pores have a diameter comprised between 5 and 100
.mu.m the porosity is comprised between 50% and 95%.
[0081] In a preferred embodiment in the macroporous polymeric
adsorbent material having a three-dimensional structure when the
interconnected pores have a diameter of 20-30 .mu.m or 5-10 .mu.m
the porosity is comprised between 80% and 90%.
[0082] The diameter of the interconnected pores is measured by
using Scanning Electron Microscopy (SEM) analysis.
[0083] Preferably n is 0%, 25%, 50%, 75%.
[0084] Preferably m is 100%, 75%, 50%, 25%.
[0085] Preferably p is 10%, 16.7%, 20%.
[0086] Preferably Y is COOCH.sub.2CH.sub.2OH,
COOCH.sub.2CH.sub.2NH.sub.2.
[0087] Preferably R is CH.sub.3
[0088] Preferably R', R'', R''', the same or different are H or
CH.sub.3.
[0089] Preferably the spacer is:
##STR00005##
[0090] Preferably q is 1, 2.
[0091] Preferably the crosslinker is selected from the group
consisting of: Divinylsulphone, N,N'-Methylenebisacrylamide,
N,N'-Methylenebismetaacrylamide, N,N'-hexamethylenebisacrylamide,
N,N'-diallylbisacrylamide, diallyl fumarate, diallyl phthalate,
ethyleneglycoldiacrylate, poly(ethyleneglycol)diacrylate,
propyleneglycoldiacrylate, poly(propyleneglycol)diacrylate.
[0092] More preferably the crosslinker is
N,N'-Methylenebisacrylamide.
[0093] In a preferred embodiment the macroporous polymeric
adsorbent material has a three-dimensional structure with
interconnected pores of diameter comprised between 20 and 30 .mu.m,
a porosity comprised between 80% and 85% and the cryogel is of
polystyrene-N-methyl-D-glucamine.
[0094] In a preferred embodiment the macroporous polymeric
adsorbent material has a three-dimensional structure with
interconnected pores of diameter comprised between 10 and 15 .mu.m,
a porosity comprised between 82% and 87% and the cryogel is of
polystyrene-N-methyl-D-glucamine and 2-hydroxyethylmethacrylate
copolymer 1:1.
[0095] The thermal degradation temperature is determined by
thermogravimetric analysis using a thermogravimetric apparatus
under a nitrogen atmosphere starting at 20.degree. C., heating rate
10.degree. C./min.sup.-1 until 600.degree. C.
[0096] Preferably, when the cryogel consists of
polystyrene-N-methyl-D-glucamine derivative polymer, the
temperature at maximum rate of decomposition of glucamine part is
around 308.degree. C. and the temperature at maximum rate of
decomposition of polystyrene matrix is around 443.degree. C.
[0097] Preferably, when the cryogel consists of
styrene-N-methyl-D-glucamine derivative/2-hydroxyethylmethacrylate
copolymer, the temperature at maximum rate of decomposition of
glucamine is around 298.degree. C. and the temperature at maximum
rate of decomposition of polymeric matrix is around 426.degree.
C.
[0098] A further object of the present invention is the process for
the preparation of macroporous polymeric adsorbent material having
a three-dimensional structure with interconnected pores of diameter
comprised between 5 and 100 .mu.m, being in the form of a cryogel,
wherein the cryogel is of formula (I):
##STR00006##
[0099] Wherein n is a percentage comprised between 0 and 99;
[0100] m is a percentage comprised between 1 and 100;
[0101] n+m is 100;
[0102] p is a value ranging from 0% to 40% of (n+m);
[0103] Y is selected from the group consisting of: COOH,
CONH.sub.2, COOCH.sub.2CH.sub.2OH, COOCH.sub.2CH.sub.2NH.sub.2,
COOCH.sub.2CH.sub.2N(CH.sub.3).sub.2, SO.sub.3H, PhSO.sub.3H,
PhCOOH;
[0104] R is selected from the group consisting of H, CH.sub.3,
CH.sub.2CH.sub.3, CH.sub.2CH.sub.2CH.sub.3, CH(CH.sub.3).sub.2;
[0105] R', R'', R''', the same or different are H or CH.sub.3;
[0106] spacer is selected from the group consisting of
##STR00007##
[0107] q is an integer comprised between 1 and 10;
[0108] A is the main polymeric chain which is repeated as indicated
in the general formula (I);
[0109] the crosslinker is a compound with two polymerizable double
bond.
[0110] Comprising the following steps: [0111] a) Mixing at least
one polymerizable monomer containing N-alkyl-D-glucamine selected
from the group consisting of:
[0111] ##STR00008## [0112] wherein R is selected from the group
consisting of H, CH.sub.3, CH.sub.2CH.sub.3,
CH.sub.2CH.sub.2CH.sub.3, CH(CH.sub.3).sub.2; [0113] R' is H,
CH.sub.3 [0114] q is an integer comprised between 1 and 10; [0115]
and optionally a polymerizable monomer not containing
N-alkyl-D-glucamine selected from the group consisting of:
[0115] ##STR00009## [0116] wherein R is selected from the group
consisting of H, CH.sub.3, CH.sub.2CH.sub.3,
CH.sub.2CH.sub.2CH.sub.3, CH(CH.sub.3).sub.2; [0117] R' is H,
CH.sub.3 [0118] q is an integer comprised between 1 and 10; [0119]
with a crosslinking agent characterised in having two polymerizable
double bonds in the presence of a solvent or mixture of solvents
being in the solid state at the temperatures used in the
cryo-polymerization process. [0120] b) Adding at a temperature
comprised between 0 and 5.degree. C., under stirring, to the
solution as obtained in step a) an initiator of radical
polymerization and a catalyst for the production of radicals.
[0121] c) Cooling of the solution as obtained in b) at a
temperature comprised between -10 and -25.degree. C. for a time
comprised between 12 and 48 hours until the cryogel is obtained;
[0122] d) Thawing, washing and drying the cryogel as obtained in
step c).
[0123] Preferably in step a) the percent molar ratio between
polymerizable monomer containing N-alkyl-D-glucamine and the
polymerizable monomer not containing N-alkyl-D-glucamine is
comprised between 1% to 100%, more preferably is 25%, 50%, 75%,
100%.
[0124] Preferably in step a) the solvent is selected from the group
consisting of: water, dimethylsulphoxide, dioxane,
N,N-dimethylacetamide, tert-butanol, cyclohexane, and mixtures
thereof, more preferably is water.
[0125] Preferably in step a) the crosslinking agent is selected
from the group consisting of: Divinylsulphone,
N,N'-Methylenebisacrylamide, N,N'-Methylenebismetaacrylamide,
N,N'-hexamethylenebisacrylamide, N,N'-diallylbisacrylamide, diallyl
fumarate, diallyl phthalate, ethyleneglycoldiacrylate,
poly(ethyleneglycol)diacrylate, propyleneglycoldiacrylate,
poly(propyleneglycol)diacrylate.
[0126] Preferably in step a) the crosslinking agent is added in a
molar ratio comprised 0 and 1/2.5 in respect to the molar amount of
starting monomers, preferably 1/6.
[0127] Preferably in step a) the concentration of all polymerizable
species is comprised between 10% and 50% in weight in respect to
the volume of used solvent.
[0128] More preferably in step a) The concentration of all
polymerizable species is comprised between 10% and 30% in weight in
respect to the volume of used solvent.
[0129] Preferably in step a) pH is maintained neutral, preferably
in the range between 6-8.
[0130] The pH can be adjusted by adding diluted acids or bases,
such as HCl and NaOH.
[0131] Preferably in step b) the initiator of radical
polymerization is a compound capable of forming radicals; more
preferably can be selected from the group consisting of organic and
inorganic peroxides, peracids, azo-compounds, redox or UV
initiators.
[0132] Preferably in step b) the initiator of radical
polymerization is used with a concentration between 0.5% and 10% by
weight, based on the sum of monomers by weight.
[0133] Preferably in step b) the catalyst for the production of
radicals is tetramethylethylenediamine.
[0134] Preferably the washing step is carried out by washing
sequentially with water, followed by diluted HCl and finally with
mixtures of H.sub.2O/HCl/EtOH wherein the concentration of EtOH
progressively increase up to pure EtOH.
[0135] Preferably the drying step is carried out under nitrogen
flow and then under vacuum.
[0136] A further object of the present invention is the use of the
macroporous polymeric adsorbent material having a three-dimensional
structure with interconnected pores of diameter comprised between 5
and 100 .mu.m, being in the form of a cryogel, wherein the cryogel
is of formula (I) for sequestering and/or removing toxic
contaminants.
[0137] Preferably for sequestering and/or removing toxic
contaminants from contaminated water.
[0138] Preferably for sequestering and/or removing toxic
contaminants from contaminated soil.
[0139] Preferably toxic contaminants are toxic metalloids and/or
toxic heavy metals.
[0140] Preferably toxic metalloids are selected from the group
consisting of arsenic, boron, antimony. More preferably boron,
arsenic.
[0141] Preferably toxic heavy metals are selected from the group
consisting of cadmium, mercury, lead, manganese, chromium, cobalt,
nickel, copper, zinc, silver, thallium. More preferably
chromium.
[0142] A further object of the present invention is the use of the
macroporous polymeric adsorbent material having a three-dimensional
structure with interconnected pores of diameter comprised between 5
and 100 .mu.m, being in the form of a cryogel, wherein the cryogel
is of formula (I) for the manufacture of devices for sequestering
toxic contaminants.
[0143] The devices can be used in any process known in the art for
sequestering toxic contaminants, preferably from water.
[0144] Preferably the devices for sequestering toxic contaminants
can be in the form of filters or sponges.
[0145] Are therefore object of the present invention the filters or
sponges comprising the macroporous polymeric adsorbent material
having a three-dimensional structure with interconnected pores of
diameter comprised between 5 and 100 .mu.m being in the form of a
cryogel, wherein the cryogel is of formula (I).
[0146] The filters can be included in filtration system for
domestic or industrial environments, can be included in water
filtering cartridges for carafes, can be included in systems for
remediation of sewage and wastewater.
[0147] Sponges can be used in soil remediation.
[0148] After remediation, the contaminants are retained by the
sponge when it is squeezed while the liquid matrix is released
clean.
EXAMPLES
Example 1: Synthesis of 4-vinyl-benzyl-N-methyl-D-glucamine
[0149] The starting monomer was synthesized by suspending
N-methyl-D-glucamine (1 g, 5 mmol) in 30 ml of CH.sub.3OH and
adding to the suspension an equimolar amount of
4-vinyl-benzylchloride (0.70 mL, 5 mmol) in presence of
Na.sub.2CO.sub.3, according to the following reaction scheme.
##STR00010##
[0150] The reaction mixture was stirred at room temperature and the
reaction progress monitored by Thin Layer Chromatography (TLC). At
the end of the reaction, the mixture was filtered and the methanol
evaporated. The product was purified by crystallization in
chloroform and characterized by Nuclear Magnetic Resonance
(NMR).
[0151] Product: 4-vinyl-benzyl-N-methyl-D-glucamine MW=311.38
g/mol
[0152] .sup.1H-NMR (400 MHz, in DMSO) [ppm referred to TMS] 2.10
(s, 3H, N--CH.sub.3); 2.4-2.6 (m 2H, N--CH.sub.2--CH); 3.31-3.84
(m, 8H, CH+CH.sub.2); 5.22 (dd, 1H, CH.dbd.CH.sub.2 cis); 5.85 (dd,
1H, CH.dbd.CH.sub.2 trans); 6.71 (dd, 1H, CH.dbd.CH.sub.2); 7.35
(m, 4H, CH aromatic).
Example 2: Synthesis of Methacrylamido Derivative of
N-methyl-D-glucamine
[0153] The monomer was synthesized by dissolving
N-methyl-D-glucamine (1 g, 5 mmol) in 25 ml of CH.sub.3OH and 5 ml
of water. At the solution kept at 0.degree. C., methacryloyl
chloride (0.48 ml, 5 mmol) was slowly added keeping the pH around
8-9 by adding few drops of 2M KOH aqueous solution according to the
following reaction scheme.
##STR00011##
[0154] After 1 h the mixture was filtered and the solvent
evaporated. The obtained product was purified by crystallization in
chloroform and characterized by NMR,
Example 3: Synthesis of Methacrylate of
N-hydroxyethyl-N-methyl-D-glucamine
[0155] The first step of this synthesis is the preparation of
2-chloroethyl-methacrylate. Methacryloyl chloride (14 g, 134 mmol)
was dissolved in 70 ml of THF and the solution was cooled to
0.degree. C. A mixture of equimolar amount of 2-chloro-ethanol (10
g, 124 mmol) and triethylamine (21 ml) was slowly added keeping the
temperature at 0.degree. C. After stirring for 1 h, the solution
was filtered, and diluted with ethyl ether and washed with water.
The solution was dried with anhydrous Na.sub.2SO.sub.4, filtered
and evaporated under vacuum. The obtained 2-chloroethylmethacrylate
was distilled under vacuum and characterized.
[0156] N-methyl-D-glucamine (1 g, 5 mmol) was suspended in 30 ml of
methanol and an equimolar amount of 2-chloroethyl-methacrylate
(0.74 ml, 5 mmol) was added. Anhydrous Na.sub.2CO.sub.3 was added
and the mixture was stirred for 7 hours at room temperature. After
filtration and solvent evaporation the product was crystallized in
chloroform and characterized by NMR.
[0157] The reaction is showed in the following reaction scheme.
##STR00012##
Example 4: Cryo-Polymerization
[0158] In a 1.5 mL vial containing 180 .mu.L of H.sub.2O, 40 mg of
4-vinyl-benzyl-N-methyl-D-glucamine and 3.3 mg of
N,N'-methylenebisacrylamide (MBAA, molar ratio 1/6 comparing to the
moles of monomer) were added. Syntheses of copolymeric materials
with HEMA as co-monomer were performed using following molar ratio:
25/75, 50/50, 75/25. To the reaction mixture, HCl 2N was added at
small doses, controlling the pH until reaching neutrality (about 50
.mu.L) and stirring until complete dissolution. Additional 24 .mu.L
of H.sub.2O were added, then the solution was cooled to 0.degree.
C. and 3 .mu.L of a 10% w/v ammonium persulphate (APS) solution and
3 .mu.L of a 10% w/v tetramethylethylenediamine (TEMED) solution
were added respectively under vigorous stirring. The reaction
mixture was stirred for about 1 min and then transferred to a
micro-reactor with a diameter of about 5.5 mm pre-cooled to
0.degree. C. The reactor was placed in a cryostat at -14.degree. C.
for about 24 hours, then, after thawing, the cryogel obtained was
washed with H.sub.2O then with HCl 0.5 M and finally with mixtures
of H.sub.2O/HCl/EtOH progressively increasing the concentration of
EtOH up to pure EtOH. The purified cryogel was dried under nitrogen
flow and then under vacuum. The final product consists of
macroporous monolithic cryogel that is ready for the capture of
arsenic, boron and toxic heavy metals ions from water.
[0159] The following formulas show examples of the structure of the
cryogel obtained.
##STR00013##
Example 5: SEM Analysis
[0160] Scanning Electron Microscopy (SEM) analysis was performed by
using a Zeiss Supra 25 field emission microscope. All samples were
previously coated with a thin layer of gold (<10 nm) in order to
make them conductive. FIG. 1 shows the micrographs of the all
synthesized cryogels. In particular, all samples reveal a typical
macroporous structure. Furthermore, it is possible to observe from
FIGS. 1 (A) and (B) that when HEMA is absent or its concentration
is low, the pore distribution appears more uniform and regular
ranging from 20 to 30 .mu.m. Vice versa, cryogel with a higher
content in HEMA [FIG. 1 (C) and (D)] show a more jagged porous
structure with smaller pore sizes. In the insets of FIGS. 1
(A)-(D), high-magnification images of the surfaces of cryogels are
reported. From the inspection of the images, it is possible to
appreciate the more uniform distribution and shape of the pores on
their surface by decreasing the HEMA content.
Example 6: Thermogravimetric Analyses
[0161] Thermogravimetric analyses (TGA) of the cryogel were
performed by using a thermogravimetric apparatus (TA Instruments
Q500) under a nitrogen atmosphere starting at 20.degree. C.,
10.degree. C./min.sup.-1 heating rate until to 600.degree. C. The
FIG. 2 shows the TGA results deriving from
Polystyrene-N-Methyl-D-glucamine derivate and the related copolymer
containing the 50% HEMA. It is possible appreciate that both
samples undergo to two separate thermal degradation steps beginning
from 280.degree. C. up to 500.degree. C. The first thermal
degradation steps belonging to polystyrene-N-Methyl-D-glucamine and
co-poly(styrene-N-methyl-D-glucamine--HEMA) samples can be assigned
to the decomposition of glucamine part (308 and 298.degree. C.
respectively) of the polymers. At higher temperature, the thermal
degradation of polystyrene-N-Methyl-D-glucamine and
co-poly(styrene-N-Methyl-D-glucamine--HEMA) takes place with a
temperature at maximum rate of decomposition of 443 and 426.degree.
C. respectively.
Example 7: NMR Characterization
[0162] .sup.1H-NMR Proton nuclear magnetic resonance and HMBC
(Heteronuclear Multiple Bond Correlation) spectra (FIGS. 3 and 4),
were recorded in order to characterize the purified
styrene-N-methyl-D-glucamine monomer synthetized by reaction of
4-vinylbenzyl-chloride and N-methyl-D-glucamine. By the combination
of the mono- and bi-dimensional analysis it is possible to confirm
the presence of a para-substituted aromatic ring linked to the
glucamine molecule. Furthermore, in the .sup.1H-NMR spectrum, in
the region between 5.0 and 7.0 ppm and 2.5-3.8 ppm are observable
the diagnostic peaks of the C.dbd.C bond and the typical overlapped
aliphatic hydrogen signals respectively.
Example 8: FTIR Analysis
[0163] FTIR (Fourier Transform Infrared Spectroscopy) analysis was
performed for the polystyrene-N-methyl-D-glucamine cryogel sample
(FIG. 5). The diagnostic bands at 3400-3100, 3000-2780, 1650, 1082
and 1024 cm.sup.-1, corresponding to the O--H, C--H, C.dbd.O, and
C--O group stretching vibrations and O--H bending modes
respectively are evident. While, in the regions at 1600-1475
cm.sup.-1 and 1450-1390 cm.sup.-1 are shown the typical C.dbd.C
aromatic stretching and the tertiary and secondary C--N stretching
modes.
Example 9: Sequestration of Arsenic
[0164] The efficiency of synthesized cryogels for the sequestration
of arsenic from water was evaluated using two different
concentrations of Na.sub.2HAsO.sub.4.7H.sub.2O. Particularly, high
concentrations of arsenate ions equal to 1400 ppm and 140 ppm were
used in order to identify the maximum adsorption capacity of the
materials. The adsorption tests of the most efficient material
(material 1) were carried out using approximately 10 mg of sample
for 5 mL of solution measuring the residual concentration of
arsenic as a function of time, by ICP-MS. The results are shown in
FIG. 6.
[0165] Analysing the test with the highest concentration of
arsenic, it is possible to extrapolate a saturation value greater
than 70 mg/g. The test carried out at a concentration of arsenate
equal to 140 ppm shows that 10 mg of material are able to eliminate
99.8% of the arsenic present in the solution. Finally, to evaluate
the use of these materials in real conditions, a test at
concentration equal to 45 ppb, that is a value 4.5 times higher
than the limit of 10 ppb established by the WHO was performed. The
material deriving from 100% styrene-N-methyl-D-glucamine monomer
(material 1) and the compound made of an equimolar mixture of
styrene-N-methyl-D-glucamine and hydroxyethyl-methacrylate
(material 2) were both able to reduce arsenic concentration below
the limits of potability. Precisely, residual arsenic content of 2
ppb for material 1 and 4 ppb for material 2, as shown in the
following table 1, reporting residual values of As(V) ions after
water treatment with cryogel 1 and 2, measured by ICP-MS
technique.
TABLE-US-00001 TABLE 1 INITIAL CONC. FINAL CONC. Sample .mu.g/L As
.mu.g/L As Material 1 45.0 1.9 .+-. 0.5 Material 2 45.0 4.0 .+-.
0.5
Example 10: Sequestration of Chromium
[0166] The efficiency of synthesized cryogels for the sequestration
of chromium from water was evaluated preparing a solution of
K.sub.2Cr.sub.2O.sub.7 with an initial concentration in Cr ions of
45 ppb. The material deriving from 100%
styrene-N-methyl-D-glucamine monomer (material 1) and the compound
made of an equimolar mixture of styrene-N-methyl-D-glucamine and
hydroxyethyl-methacrylate (material 2) were both able to reduce
chromium concentration below the limits of potability. Precisely,
residual chromium content of 0.7 ppb for material 1 and 2.9 ppb for
material 2, as shown in the following table 2, reporting residual
values of Cr(VI) ions after water treatment with cryogel 1 and 2,
measured by ICP-MS technique.
TABLE-US-00002 TABLE 2 INITIAL CONC. FINAL CONC. Sample .mu.g/L Cr
.mu.g/L Cr Material 1 45.0 0.7 .+-. 0.5 Material 2 45.0 2.9 .+-.
0.5
Example 11: Equilibrium Retention Capacity
[0167] Batch equilibrium tests were carried out to calculate the
equilibrium retention capacity (Q.sub.e) values as well as the
metal ions removal percentage. In general, .about.10 mg of Material
1 were immersed into either bichromate (K.sub.2Cr.sub.2O.sub.7) or
arsenate (Na.sub.2HAsO.sub.4.7H.sub.2O) solutions (5 mL and pH=6)
at different initial concentration, ranging from 30 to 1400 mg/L
(of arsenate or chromium salt). The vials were maintained under
constant shaking at 25.degree. C. and 180 rpm for 24 h, withdrawing
aliquots of 100 .mu.L at different intervals of time to perform
kinetic studies. The residual metal ion concentrations were
evaluated by ICP-MS measurements. All experiments were repeated
three times reporting a maximum Relative Standard Variation of 5%
for As(V) and Cr(VI).
[0168] The following table 3 shows the initial concentration of
metal ions (CO), at the equilibrium (Ce), the equilibrium removal
capacity (Q.sub.e) calculated from the pseudo-second order model
fitting, and percentage of metal ions removal after 24 h of contact
time at room temperature wherein retention is calculated by the
formula
C 0 - C e C 0 .times. 100 ##EQU00001##
[0169] From the data of table 3 it is clear that all batch
experiments showed highly efficient removal of both As(V) and
Cr(VI) for all concentration studied, excepted for the highest
ones, due to the reaching of cryo-sponge saturation limit.
TABLE-US-00003 TABLE 3 As(V) Cr(VI) C.sub.e Q.sub.e C.sub.e Q.sub.e
C.sub.0 (mg (mg (mg Retention C.sub.0 (mg (mg (mg Retention
L.sup.-1) L.sup.-1) g.sup.-1) % L.sup.-1) L.sup.-1) g.sup.-1) % 7.7
0.3 4.2 97.6 7.9 0.1 10.2 98.5 17.4 0.5 7.7 97.3 18.1 0.2 18.3 98.9
72.6 1.5 36.5 97.9 68.3 1.3 59.9 98.1 168.4 18.6 69.4 88.9 165.1
10.7 122.5 93.5 338.8 182.5 73.7 46.2 308.1 190.2 125.4 37.1
[0170] Q.sub.e values for both metal ions were used to calculate
the maximum adsorption capacities (Q.sub.m) based on Langmuir
model. From data fitting, (Q.sub.m) values for As(V) and Cr(VI)
were respectively 76.3 and 130.8 (mg g.sup.-1). As showed in the
following Table 4, data obtained from the material 1 were
significantly higher than other reported in the prior art where
similar material were used to remove As(V) or Cr(VI) ions.
TABLE-US-00004 TABLE 4 NMG-based As(V) Q.sub.m Cr(VI) Q.sub.m Time
of Year materials (mg g.sup.-1) (mg g.sup.-1) contact Prior art
2020 VbNMG-100 76.3 130.8 24 h Material 1 2014 Grafted NMDG 67.1 /
/ [N.R Shinde] membrane 2012 PVbNMDG 55.2 / 48 h [B.F Urbano]
nanocomposite 2004 NMDG 60.5 / 3 d. [L. Dambies] 2004 IRA 743 14.7
/ 3 d. [L. Dambies] 2010 IRA-743 / 29.3 1 h [M.R Gandhi]
Example 12: Interfering Tests
[0171] For the interfering tests, in order to obtain the final
concentrations of 0, 15, 30, 60, 120, 240 and 480 mg/L of sulphate
or phosphate salt and 30 mg/L of arsenate or chromium salt, seven
different vials containing 500 .mu.L of arsenate salt (60 mg/L) or
chromium salt (60 mg/L) solution were mixed with 500 .mu.L of
sulphate or phosphate at increasing concentrations (0, 30, 60, 120,
240, 480 and 960 mg/L). In each vial, a weighted sample of material
1 was added and shaken up to 24 h at 25.degree. C. and 180 rpm.
After that, ICP-MS of As(V), Cr(VI) and P(V) residues was carried
out, whereas the contribution of sulphate ions to As(V) or Cr(VI)
was extrapolated by difference. After 24 h of material 1/solution
contact time, ICP-MS measurements evidenced that the presence of
phosphate did not affect the As (V) and Cr(VI) sorption process of
the material 1 for all oxyanion concentration tested, maintaining
high sorption retention (.about.99%). Conversely, both As(V) and
Cr(VI) retention were influenced by the presence of sulphate ions.
In particular, by adding concentration of sulphate of 60 mg/L, the
material 1 reduces its efficiency to 80% for both ions.
Example 13: Reusability
[0172] To study the reusability of the cryogel, material 1 was
subjected to six consecutive adsorption/desorption cycles.
Specifically, 30 mg/L of arsenate solution was added drop by drop
to .about.134 mg of sponge to reach the maximum swollen degree.
After 5 minutes of contact time, the sponge was squeezed,
withdrawing arsenate solution. Then, the material 1 was kept
between two foils of cellulose paper for 10 minutes to remove the
excess of arsenate solution before adding the fresh one. The
content of As (V) in the water residue collected after each
squeezing cycle was measured by ICP-MS revealing the .about.99% of
arsenic removal up to six cycles.
[0173] To evaluate the complete regeneration of material 1,
recycling tests by washing in acidic media the sample were carried
out. To this purpose, the material 1 was kept in contact for 24 h
with 30 mg/L of arsenate solution. After that, the sponge was
regenerated in a column with HCl 1M and washed with water to reach
pH=6. The experiment was repeated up to three subsequent cycles.
After each cycle both acid and residue arsenate solutions were
analysed by ICP-MS revealing As desorption values higher than 60%,
and thus an efficient reusability of the regenerated sponge for all
tested cycles was found.
* * * * *